There has heretofore been known a double-structured aerosol can containing, in a single aerosol container, a first agent containing a strongly alkaline component and a second agent comprising an acid component that compose an oxidizing hairdye in an attempt to eject these agents simultaneously.
As for the oxidizing hairdye contained in the double-structured aerosol can, the first agent comprises a dye and a strongly alkaline component which is chiefly an ammonia component. If the component in the first agent comes in contact with oxygen in the air during the storage, the first agent is chemically degenerated and its dyeing function decreases. If it continues to be in contact with oxygen, then the hair can no longer be dyed. Therefore, the internal pouch for containing the first agent must have a high degree of oxygen shut-off property (barrier property) and must also work to prevent the content from volatilizing out of the internal pouch and from extinguishing. Namely, the internal pouch must have a high gas shut-off function. It is also required to prevent the layer materials from being corroded or from being peeled off by the strongly alkaline component.
The second agent is an oxidizing acid component which chiefly comprises hydrogen peroxide. Therefore, the internal pouch must have a resistance against the pressure of internal expansion due to oxygen generated by the decomposition of hydrogen peroxide which is the oxidizing agent and must, further, work to prevent the content from volatilizing out of the internal pouch and from extinguishing. Further, the pouch must also be capable of preventing the layer materials from being corroded or from being peeled off like the internal pouch for the first agent.
As the internal pouches adapted to the first agent and the second agent of the oxidizing hairdye contained in the double-structured aerosol can, therefore, the present inventors have proposed the internal pouches held in the double-structured hairdye aerosol can in which the individual internal pouches were constituted by laminated layers of a metal foil and a thermoplastic resin or thermoplastic resin layers, and at least either one of the internal pouches was constituted by laminated layers of the metal foil and the thermoplastic resin (patent document 1).